Joining two concentric cylinders may be used, for example, in joining two rotors for the assembly of a steam or gas turbine. Another example may include joining two pipes in a piping system. Joining two concentric cylinders may require adjusting the combined length of the two concentric cylinders after the two concentric cylinders have been aligned. By inserting a spacer between the end surfaces of two concentric cylinders being joined, the width of the spacer may be used to adjust the combined length of the two concentric cylinders. Different widths of the spacer may be used to adjust the combined length either by machining the spacer or swapping out a different spacer with the required width. However, a unitary spacer between the two cylinders cannot be inserted and/or removed from between the two concentric cylinders without disturbing the alignment.